You make a good point; thank you. Self-education (as opposed to helping others to learn) is not to be scorned. But if I do nothing but improve my skills, never employing them usefully, then I'd file this under self-amusement.

I have already had an engineering career. While I was paid well I did not feel I was paid for doing good work; rather, I was pressured to do poor work and commit fraud against our customers. I no longer have any interest in engineering for pay, therefore none in making myself attractive to potential clients. My motivator today is a desire to be useful.

I would do a disservice to the aspiring young engineer if I did not admit that free software projects are an excellent route to a fatter portfolio.